Diphtheria (dif-THEER-e-uh) is an infection of the lining of the upper respiratory tract (the nose and throat). It is a serious disease that can cause breathing difficulty and other complications, and it can be fatal. Routine vaccination * against diphtheria has made it rare in the United States.

What Is Diphtheria?

Diphtheria is an infection caused by a bacterium called Corynebacterium diphtheriae (kor-ih-nee-bak-TEER-e-um dif-THEER-e-eye) that infects the upper respiratory tract. As the bacteria infect the nose, throat, or larynx (LAIR-inks; also called the voice box), a distinctive thick membrane forms over the site of infection. The membrane can become large enough to interfere with a person's ability to breathe and swallow. Some strains of C. diphtheriae produce an exotoxin * that can cause arthritis and can damage the nerves and heart. Sepsis, a potentially serious spreading of infection (usually bacterial) through the bloodstream and body, can result from diphtheria, causing shock * , heart failure, and even death.

How Common Is Diphtheria?

Diphtheria occurs throughout the world and is common in developing regions of Africa, Asia, and South America, where children often do not receive the diphtheria vaccine. Cases usually occur in winter and the cooler months of autumn and spring.

Diphtheria infection is extremely rare in the United States because of the widespread use of childhood diphtheria vaccination. From 1994 through 2014, 15 cases of diphtheria were reported in the United States, with only one death. However, a diphtheria epidemic * continues to affect India, which has improved rates significantly since the 1980s, but still recorded approximately 7,000 cases in 2014 and 2,350 cases in 2015.

Is Diphtheria Contagious?

Diphtheria is highly contagious. An untreated person who has diphtheria can spread the infection for up to one month. Within 48 hours of receiving antibiotics, however, people infected with diphtheria are usually no longer contagious.

The bacteria that cause diphtheria are spread through the air in drops of moisture from the respiratory tract, often from coughing or sneezing. Sharing drinking glasses or eating utensils, or handling soiled tissues or handkerchiefs that have been used by a person with the disease can also transmit the bacteria. A person can get diphtheria from someone who has symptoms of the disease or from someone who is just a carrier * of the bacteria.

How Do People Know They Have Diphtheria?

Within five days after becoming infected, a person typically begins to show symptoms of diphtheria. Early symptoms often include a severe sore throat, runny nose, mild fever, and swollen glands in the neck. People infected with diphtheria in the nose, throat, or larynx usually develop a thick membrane at the site of the infection. Membranes in the nose are often white, whereas those at the back of the throat are gray-green.

As diphtheria progresses, respiratory symptoms can become more severe and include difficulty breathing or swallowing and a bark-like cough. Sometimes inflammation and swelling in the throat and the diphtheria membrane itself can cause blockage of the upper airways, making emergency treatment necessary.

How Do Doctors Diagnose and Treat Diphtheria?


Diphtheria is diagnosed when the membrane that signals the disease is seen in the nose or throat during an examination of someone with symptoms of the disease. The diagnosis is confirmed by taking a swab of the coating from underneath the membrane and performing a laboratory test that identifies diphtheria bacteria.

Canine Heroes

During the winter of 1925, a diphtheria epidemic swept through Nome, Alaska. The antitoxin was located almost 1,000 miles (1,610 kilometers) away in the city of Anchorage. The only way to transport the medicine was by dogsled. A relay of sled-dog teams, with the last leg led by a dog named Balto, carried the medicine successfully through frigid temperatures in time to save many lives. In honor of that achievement, a statue of Balto was erected in Central Park in New York City.


Hospitalized people who are known to have diphtheria are isolated to prevent the disease from spreading to others. Patients are treated in the hospital with antibiotics and diphtheria antitoxin * . The antitoxin, which is produced in horses, is given intravenously (directly into a vein).

In severe cases of diphtheria, patients may need a ventilator (VENtuh-lay-ter) to help with breathing or medication to treat complications of the disease, such as septic shock * , heart inflammation, or heart failure. After they leave the hospital, bed rest at home for several weeks is generally recommended. Members of the same household are usually given a diphtheria booster vaccine to protect against possible infection. Recovery from diphtheria often takes four to six weeks or more.


Complications of diphtheria include abnormal heart rhythms, arthritis, and neuritis * . Diphtheria is most dangerous for children younger than five years old and older adults. Death occurs in up to 10 percent of people with diphtheria who receive medical treatment; death rates are higher in some parts of the world where treatment is not readily available.

Can Diphtheria Be Prevented?

In the United States, immunization programs have been very effective in preventing diphtheria. The diphtheria vaccine is given in combination with vaccines for tetanus * and pertussis * (called the DTaP vaccine) as part of a child's routine immunizations. Four doses of the vaccine are given before the child is two years old. The first booster dose is given at four to six years of age when a child enters school. Additional booster doses are recommended every 10 years, in combination with a tetanus booster.

Diphtheria Vaccine by Age and Type

Diphtheria Vaccine by Age and Type
SOURCE: Centers for Disease Control and Prevention. “Vaccines and Immunizations.” http://www.cdc.gov/vaccines/vpdvac/pertussis/default.htm#vacc (accessed August 20, 2015). Table by Cenveo Publisher Services. © 2016 Cengage Learning®.

NOTE: Upper-case letters in these abbreviations denote full-strength doses of diphtheria (D) and tetanus (T) toxoids and pertussis (P) vaccine. Lowercase “d” and “p” denote reduced doses of diphtheria and pertussis used in the adolescent/adult-formulations. The “a” in DTaP and Tdap stands for “acellular,” meaning that the pertussis component contains only a part of the pertussis organism.

Sometimes people have mild reactions to the vaccine, including a low-grade fever, tenderness at the injection site, and irritability. Very rarely, stronger reactions such as seizures * or allergic reactions can occur.

See also Bacterial Infections • Vaccines and Immunization



Centers for Disease Control and Prevention. 2015. “Diphtheria.” In Epidemiology and Prevention of Vaccine-Preventable Diseases. 13th ed. http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/dip.pdf (accessed December 4, 2015).

College of Physicians of Philadelphia. “History of Diphtheria.” The History of Vaccines. http://www.historyofvaccines.org/content/timelines/diphtheria (accessed December 4, 2015).


Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30333. Toll-free: 800-311-3435. Website: http://www.cdc.gov (accessed December 4, 2015).

Immunization Action Coalition. 2550 University Ave. W, Suite 415N, St. Paul, MN 55114. Telephone: 651-647-9009. Website: http://www.immunize.org (accessed December 4, 2015).

World Health Organization. Ave. Appia 20, 1211 Geneva 27, Switzerland. Telephone: 41-22-791-21-11. Website: http://www.who.int/en (accessed December 4, 2015).

* vaccination (vak-sih-NAY-shun) is a preparation of killed or weakened germs, or a part of a germ or product it produces, that is given (usually by an injection) to prevent or lessen the severity of the disease caused by that germ. Also called immunization.

* exotoxin (ek-so-TOK-sin) is a substance produced by bacteria that has harmful effects on the infected person.

* shock is a serious condition in which blood pressure is very low and not enough blood flows to the body's organs and tissues. Untreated, shock may result in death.

* epidemic (eh-pih-DEH-mik) is an outbreak of disease, especially an infectious disease, in which the number of cases suddenly becomes far greater than usual. Usually epidemics are outbreaks of diseases in specific regions. Widespread epidemics are called pandemics.

* carrier is a person who has a bacterium, virus, or gene for a disease in his or her body that can be transmitted to other people without getting sick himself or herself.

* antitoxin (an-tih-TOK-sin) is an agent that counteracts the effects of toxins, or poisons, on the body. It is produced to act against specific toxins, such as those made by the bacteria that cause botulism or diphtheria.

* septic shock is shock resulting from overwhelming infection. It is characterized by decreased blood pressure, internal bleeding, heart failure, and, in some cases, death.

* neuritis (nuh-RYE-tis) is an inflammation of the nerves that disrupts their function.

* tetanus (TET-nus) is a serious bacterial infection that affects the body's central nervous system.

* pertussis (per-TUH-sis) is a bacterial infection of the respiratory tract that causes severe coughing.

* seizures (SEE-zhurs) are sudden bursts of disorganized electrical activity that interrupt the normal functioning of the brain, often leading to uncontrolled movements in the body and sometimes a temporary change in consciousness.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)